Flask



FIG. 1 is a top rear perspective view showing the new design for aflask;

FIG. 2 is a front view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof;

FIG. 7 is a rear view thereof; and,

FIG. 8 is a bottom rear perspective view thereof.

CLAIM The ornamental design for a flask, as shown and described.